A paved surface is always subjected to external actions of traffic loads, weather conditions or the like and also due to aged deterioration (obsolescence) and others, and consequently a service use property thereof would be lowered, if it is left as it is. Accordingly, if the maintenance and administration thereof are not sufficient, it is difficult to ensure smooth and safe traffic or transportation. Therefore, it is necessary to carry out proper maintenance and administration.
For observation of the road condition, there was a method for utilizing a road surface photography taken by a hand held camera, but it was inefficient and unpractical.
For this reason, the applicants of the present application have invented an apparatus for continuously photographing a road surface (Japanese Patent Publication Sho No. 44-25737 publication) and thereby the foregoing problem of the conventional example has been solved.
However, this road surfacial continuous photographing apparatus is so arranged that a film feed speed may be controlled by a synchro transmitter which is operable in conjunction with a vehicle axle and in addition a light intensity of a road surface light projector may be controlled by a generator which is operable in conjunction with the vehicle axle, and consequently there have been involved the following problems. Namely, since the light intensity control of the light projector is carried out according to a vehicle speed, a large-sized and large electric power control apparatus is required, and thereby there has been raised beside such a problem that the apparatus itself is very expensive, such a problem that the same occupies a space in the interior of a narrow room of a vehicle, and also there has been raised such a problem that because of the complicated apparatus the frequency of maintenance and inspection thereof becomes high.
In addition, since the light intensity of the light projector is controlled according to the vehicle speed, there has been raised such a problem that the lifetime of a lamp of the light projector is short.
Furthermore, even if the speed of the vehicle is constant, a rotation speed of the vehicle axle is varied with the number of gears and gear ratios of a driving apparatus or, in addition, kinds of tires and air pressures of the tires, etc., so that there has been brought about such a problem that on loading the road surfacial continuous photographing apparatus on the vehicle adjusting of the apparatus or changing in a design of the apparatus becomes necessary for each vehicle.
Accordingly, a purpose of this invention is to provide an apparatus for continuously photographing a road surface which is free from the problems of the foregoing conventional example by controlling an iris and a film feed speed of a motion picture camera according to a vehicle speed, and thereby making constant a light intensity from a light projector.
Another purpose of this invention is to provide an apparatus for continuously photographing a road surface which is free from the problems of the foregoing conventional example by obtaining a vehicle speed from a non-contact type optical sensor.